[tt] BBC: Hints of 'time before Big Bang'

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Hints of 'time before Big Bang'
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/7440217.stm
Published: 2008/06/06 14:43:18 GMT
[Thanks to Sarah for this. I never know whether the disputes over the 
arrow of time are genuine. Mario Bunge liked to point out that, just 
because certain *processes* are reversible doesn't mean the universe is.]

By Chris Lintott
Co-presenter, BBC Sky At Night, St Louis, US

A team of physicists has claimed that our view of the early Universe
may contain the signature of a time before the Big Bang.

The discovery comes from studying the cosmic microwave background
(CMB), light emitted when the Universe was just 400,000 years old.

Their model may help explain why we experience time moving in a
straight line from yesterday into tomorrow.

Details of the work have been submitted to the journal Physical
Review Letters.

The CMB is relic radiation that fills the entire Universe and is
regarded as the most conclusive evidence for the Big Bang.

Although this microwave background is mostly smooth, the Cobe
satellite in 1992 discovered small fluctuations that were believed
to be the seeds from which the galaxy clusters we see in today's
Universe grew.

Every time you break an egg or spill a glass of water you're
learning about the Big Bang
Professor Sean Carroll,
California Institute for Technology

Dr Adrienne Erickcek, and colleagues from the California Institute
for Technology (Caltech), now believes these fluctuations contain
hints that our Universe "bubbled off" from a previous one.

Their data comes from Nasa's Wilkinson Microwave Anisotropy Probe
(WMAP), which has been studying the CMB since its launch in 2001.

Their model suggests that new universes could be created
spontaneously from apparently empty space. From inside the parent
universe, the event would be surprisingly unspectacular.

Arrow of time

Describing the team's work at a meeting of the American Astronomical
Society (AAS) in St Louis, Missouri, co-author Professor Sean
Carroll explained that "a universe could form inside this room and
wed never know".

The inspiration for their theory isn't just an explanation for the
Big Bang our Universe experienced 13.7 billion years ago, but lies
in an attempt to explain one of the largest mysteries in physics -
why time seems to move in one direction.

The laws that govern physics on a microscopic scale are completely
reversible, and yet, as Professor Carroll commented, "no one gets
confused about which is yesterday and which is tomorrow".

Physicists have long blamed this one-way movement, known as the
"arrow of time" on a physical rule known as the second law of
thermodynamics, which insists that systems move over time from order
to disorder.

This rule is so fundamental to physics that pioneering astronomer
Arthur Eddington insisted that "if your theory is found to be
against the second law of thermodynamics I can give you no hope;
there is nothing for it but to collapse in deepest humiliation".

The second law cannot be escaped, but Professor Carroll pointed out
that it depends on a major assumption - that the Universe began its
life in an ordered state.

This makes understanding the roots of this most fundamental of laws
a job for cosmologists.

"Every time you break an egg or spill a glass of water you're
learning about the Big Bang," Professor Carroll explained.

Before the bang

In his presentation, the Caltech astronomer explained that by
creating a Big Bang from the cold space of a previous universe, the
new universe begins its life in just such an ordered state.

The apparent direction of time - and the fact that it's hard to put
a broken egg back together - is the consequence.

Much work remains to be done on the theory: the researchers' first
priority will be to calculate the odds of a new universe appearing
from a previous one.

In the meantime, the team have turned to the results from WMAP.

Detailed measurements made by the satellite have shown that the
fluctuations in the microwave background are about 10% stronger on
one side of the sky than those on the other.

Sean Carroll conceded that this might just be a coincidence, but
pointed out that a natural explanation for this discrepancy would be
if it represented a structure inherited from our universe's parent.

Meanwhile, Professor Carroll urged cosmologists to broaden their
horizons: "We're trained to say there was no time before the Big
Bang, when we should say that we don't know whether there was
anything - or if there was, what it was."

If the Caltech team's work is correct, we may already have the first
information about what came before our own Universe.